1. Field of the Invention
The invention relates to a method for repairing sewer pipes, wherein a liner is cemented to the interior of the existing sewer pipe.
2. Description of the Prior Art
Repairing sewer pipes which have developed leaks has proven to be an expensive operation, normally involving disruption of sewer service. One of the most common solutions has been to dig up the section of leaking sewer pipe and then replace it with new pipe which is suitably attached to the existing sewer pipe. The expense of this method is readily apparent, as is the disruption of sewer service.
U.S. Pat. No. 3,834,422, issued to Richard E. Larson, on Sept. 10, 1974, discloses an apparatus for internally repairing leaks in concrete sewer pipes which uses an expandable grouting sleeve and associated apparatus which are all located within the interior of the sewer pipe to be repaired. This apparatus is representative of the many available devices for internally repairing sewer pipe leaks. In addition to the complexity of devices of this type, including the expense of manufacturing and operating these devices, another disadvantage in using these apparatus is that the entire sewer pipe is blocked, whereby sewer service is disrupted while these apparatus repair the leaks in the sewer pipe. A further disadvantage of these devices is that repairs may be affected in only a relatively small localized region of the sewer pipe. Many localities have in the past used large diameter steel sewer pipes which have become corroded, whereby these steel sewer pipes have developed leaks throughout major portions of the length of the sewer pipe. Thus, the use of such devices as disclosed in U.S. Pat. No. 3,834,422 is not feasible to repair these corroded steel sewer pipes.
Many examples of apparatus for forming a sewer pipeline in situ are to be found in the prior art; e.g., U.S. Pat. No. 3,205,550 issued to Floyd E. Martin on Sept. 14, 1965, and U.S. Pat. No. 3,551,537 issued to Larry V. Thomason on Dec. 29, 1970. These apparatus are utilized when the existing, leaking sewer pipe is dug out of the ground, and rather than place new sections of sewer pipe in the ground, these apparatus are used to form a continuous section of new sewer pipe. The major disadvantage in using these apparatus to repair sewer pipes is that, in addition to the great expense involved in digging up the existing sewer pipeline, there is a complete disruption of sewer line service.
U.S. Pat. No. Re. 27,144 issued to Rubenstein, is an example of a technique for the manufacture of a reinforced composite concrete pipeline in situ. A reinforced pipe formed at the site of the pipeline is placed in a trench and a concrete is deposited around the pipe while air pressure is maintained within the pipe. Numerous different cement compositions are disclosed as being suitable substituent materials for the concrete which is deposited around the pipe, including oxysulfate and oxychloride cements. Again, the major disadvantage in using this apparatus is that the old sewer line must be completely dug up with the attendant expense and disruption of sewer line service resulting from the use of this apparatus.
Recently, it has been suggested to insert a plastic liner within an existing, but leaking, sewer pipe and attaching this liner to the existing sewer pipe by filling with concrete the space between the liner and the sewer pipe. This method is particularly suitable for repairing corroded steel sewer pipes and cracked fiberglass sewer pipes. However, many problems have been found to exist in attempting to use such a method. In order to facilitate the insertion of the plastic liner into the existing sewer pipe, it has been necessary to use a plastic liner having a small wall thickness, such that the liner has a high degree of flexibility and elasticity. The thin-walled nature of the plastic liner being used also has the additional advantage that it is more economical to manufacture. However, the major problem which precludes using this method in repairing sewer pipelines is directly attributable to the necessity of using such a flexible liner. The preferred liner cannot withstand a pressure substantially in excess of five pounds per square inch of surface area or, if that pressure limit is exceeded, the plastic liner will collapse, thereby obstructing the sewer pipe.
The space between the liner and the existing sewer pipe must be filled with cement in order to prevent the existing sewer pipe from developing further leaks and to protect the liner from being damaged. For example, leaking fiberglass sewer pipes usually experience collapsing at the topmost portion of the sewer pipe due to point-loading on that portion of the sewer pipe caused by the earth overlaying the sewer pipe. This point-load collapsing could continue once a liner has been inserted into the sewer pipe if the space between the liner and the sewer pipe is not filled with cement, whereby ground water and the earth above the sewer pipe could flow into the space between the liner and the sewer pipe. This potential erosion problem not only could cause the earth located above the sewer pipe to be subject to collapsing, but the ground water and earth flowing into the space would eventually flow to a sewage treatment plant located at the end of the sewer pipeline. This undesired ground water and earth may cause the sewage treatment plant capacity to be exceeded, whereby the dumping of untreated sewage into a river, lake, or stream might be necessitated. Additionally, if the space between the liner and the sewer pipe is not filled with cement, the ground water and earth could flow into that space and puncture, or otherwise damage, the thin-walled liner, whereby the undesired ground water and earth could enter the sewer pipeline system.
The use of conventional cements to fill the space between the liner and the existing sewer pipe presented numerous problems when attempting to cement the plastic liner to the existing sewer pipeline. The conventional cements would either shrink or swell upon curing, thereby leaving voids between the liner and the sewer pipeline or exerting excessive pressure upon the liner resulting in its collapsing or rupturing. Some conventional cements experience an exothermic reaction upon curing, whereby the excessive amounts of heat given off by these reactions damaged the plastic liner. Other cements require large amounts of pressure to pump the cement mixture into the space between the liner and sewer pipe, whereby the liner ruptured under the excessive amount of pressure.
Another major disadvantage of this method is that the existing sewer pipeline must be cleaned of the refuse and debris contained in the bottom of the sewer pipeline. This cleaning step is necessitated by the fact that conventional cements would not cure properly if the refuse found in the sewer pipeline was mixed with the cement being pumped about the liner. Additionally, sewer line service had to be disrupted while cement was being pumped into the space between the liner and the pipeline, so as to avoid the mixing of the sewer pipe refuse and the cement.
Accordingly, prior to the development of the present invention, there has been no method or apparatus available for efficiently and economically repairing a leaking sewer pipeline which does not have the problems previously described. Therefore, the art has sought an efficient and economic method for repairing sewer pipelines absent the problems of previously proposed sewer pipeline repairing methods.